Laminated film with stretched layer

ABSTRACT

Disclosed is a film ( 10 ) for the wrapping of objects. The film comprises a first film layer ( 12 ) made from an elastic material, a second film layer ( 14 ) made from a sturdy material, and a third layer ( 12 ) made from an elastic material, wherein the first and third film layers ( 12, 16 ) are stretched.

TECHNICAL FIELD

The present invention relates generally to a film for the wrapping ofobjects, particularly for wrapping steel coils.

BACKGROUND ART

In prior art there is known to use various kinds of films to wrapobjects of various kinds. Depending on the intended application area,there are different restrictions and requirements placed on the filmsthat are to be used. Laminated films comprising polymeric tapes areknown, such as disclosed in EP2799237.

However, there are still problems with known solutions, for instance itcould for some application areas be beneficial to achieve a film thatprovides a tighter sealing around an object, such as for the applicationarea of wrapping steel coils.

It would be desirable if a film could be achieved which provides a goodmechanical protection and is durable, while still wrapping tightlyaround the object around which it is wrapped.

SUMMARY OF INVENTION

An object of the present invention is to overcome at least some of theproblems outlined above.

According to a first aspect, a film for the wrapping of objects isprovided, particularly for steel coils. The film comprises a first filmlayer made from an elastic material, a second film layer made from adurable material, and a third layer also made from an elastic material.The first and third film layers are stretched in a longitudinaldirection, and the second layer is disposed between the first film layerand the third film layer. By having such a film with one un-stretchedlayer with a durable material and two elastic layers that are stretched,a film is achieved that provides a good protection, while still wrappingvery tightly to the object around which it is wrapped, due to thestretched material striving to go back to its un-stretched state.

According to a second aspect, a system for manufacturing a film for thewrapping of objects is provided. The system comprises a first rollerrunning at a first speed positioned at a first position and a secondroller running at a second speed positioned at the first position, thesecond speed being higher than the first speed. The system furthercomprises a third roller running at the first speed, positioned at thefirst position, wherein the second roller is disposed between the firstand the third roller. The system further comprises laminating rollerspositioned at a second position, the second position being downstream ofthe first position. The first roller is adapted to feed a first layerfilm comprising an elastic material, the second roller is adapted tofeed a second film layer comprising a sturdy material, and the thirdroller is adapted to feed a third layer film comprising an elasticmaterial, and the laminating rollers are adapted to laminate the threelayers into a film comprising three layers. According to an optionalembodiment, the elastic layers are stretched in the feeding direction ofthe system.

According to a third aspect, there is provided a method formanufacturing a film for the wrapping of objects, comprising the stepsof providing and stretching a first film layer comprising an elasticmaterial, providing a second film layer comprising a sturdy material,and providing and stretching a third film layer comprising an elasticmaterial, wherein the second film layer is provided between the firstfilm layer and the third film layer. The method further compriseslaminating the layers together to form a laminated film. According to anoptional embodiment, the stretching is performed in the longitudinaldirection of the film.

By using a film, system or method as disclosed herein, it is possible toachieve a film for the wrapping of objects that provides a goodprotection, both mechanically and against external factors such as airand moisture, while still wrapping very tightly around the object to bewrapped.

BRIEF DESCRIPTION OF DRAWINGS

The invention is now described, by way of example, with reference to theaccompanying drawings, in which:

FIG. 1 shows a sectional view of a first embodiment of a film accordingto the present disclosure.

FIG. 2 shows a sectional view of a second embodiment of a film accordingto the present disclosure.

FIG. 3 shows a schematic view of a first embodiment of a systemaccording to the present disclosure.

FIG. 4 shows a schematic view of a second embodiment of a systemaccording to the present disclosure.

FIG. 5 shows the steps of a first embodiment of a method according tothe present disclosure.

FIG. 6 shows the steps of a second embodiment of a method according tothe present disclosure.

DESCRIPTION OF EMBODIMENTS

In the following, a detailed description of the different embodiments ofthe solution is disclosed with reference to the accompanying drawings.All examples herein should be seen as part of the general descriptionand are therefore possible to combine in any way in general terms.Individual features of the various embodiments and methods may becombined or exchanged unless such combination or exchange is clearlycontradictory to the overall function of the implementation.

Briefly described, the solution relates to a film for the wrapping ofobjects, as well as a system and method for the wrapping of objects. Thesolution is primarily intended to be used for wrapping steel coils andother similar materials, but it should be understood that the solutionmay be applicable to other types of materials as well.

The solution is intended to achieve a film that protects the wrappedobject from external forces, such as moisture, air and scraping, andthat tightly wraps around the object it is intended to protect.

This is achieved by having a film comprising at least three layers,wherein one layer is stretched (or pre-stretched) while the other twolayers are not. By stretching one layer and not the other, it ispossible to use more rigid, sturdy and durable materials for theprotective layer that provide a better mechanical protection andreinforcing properties than materials that are adapted for beingstretched. Further, by stretching one of the layers, it is possible toachieve a film that strives to go back to un-stretched state, whichmakes the film wrap more tightly around the object it is intended toprotect. This disclosure also relates to a system and method formanufacturing such a film as well. The solution will now be described infurther detail with reference to the accompanying drawings. FIG. 1 showsa film 10 according to the present disclosure comprising two layers, afirst layer 12 and a second layer 14. The first layers 12 is stretched,such that it strives to go back to its original un-stretched state. Thisentails that the film will wrap more tightly around an object than if nolayers were stretched. Meanwhile, the second layer 14 is not stretched,which entails that a sturdier and more rigid material may be used, whichprovides better mechanical protection than materials that are adapted tobe stretched.

The first layer 12 typically comprises an elastomer, such a low densitypolyethylene. The material of the first layer 12 is intended to beflexible while still providing a good protection against externalfactors, such as e.g. moisture in the air. As mentioned, the first layer12 of the film is stretched. Typically this is done during themanufacturing of the film, which will be described in more detail laterin this disclosure. The film is typically only stretched in onedirection, which is the same direction as the film is being fed duringmanufacture, which in a completed film would be seen as the longitudinaldirection.

The second layer 14 typically comprises a woven plastic material. Thesecond layer 14 is intended to provide mechanical protection, andtherefore it is sturdier, stronger and more rigid than the first layer12. Also, unlike the first layer 12, the second layer 14 is notstretched, which enables the previously mentioned use of a material thatis sturdier, stronger and more rigid.

The second layer may in some embodiments be made of polypropylene. Inother embodiments, the second layer may be made from polyethylene, bothhigh density and low density, that has been pre-stretched, which resultsin it being much less elastic, more durable and provides a bettermechanical protection than polyethylene that has not been pre-stretched.In embodiments wherein the second layer comprises polypropylene, thepolypropylene may also be pre-stretched.

The first layer 12 and the middle layer 14 are laminated together toform one film comprising two layers. Such a film will have themechanical protection provided by the second layer 14, comprising asturdy and durable material, while still wrapping very tightly aroundthe object to be wrapped due to the first layer 12 being stretched,which makes it strive to go back to its un-stretched state. The sturdymaterial may for instance be a woven plastic material. The elasticmaterial is typically an elastomer, such as low density polyethylene. Itshould be understood that the examples used herein are not to belimiting, it is possible to use other materials that have similarproperties as the examples above.

The film according to the present disclosure is typically intended forthe wrapping of steel coils. Steel coils have very sharp edges, and theweight entails that the contact pressure is very high when they arelifted, which requires a film that is both durable and flexible, whichmay be achieved as disclosed herein.

In some embodiments, the film 10 comprises three layers instead of two.This is shown in FIG. 2. In this embodiment, the film comprises twoouter layers 12 made from an elastic material, and a middle layer 14made from a sturdy material. By using one elastic layer on each side ofthe sturdy layer, the advantageous properties of the film are furtherenhanced, such that it gives a better protection and wraps tighteraround the objects intended to be wrapped.

Looking now at FIG. 3, a system for manufacturing a film will now bedescribed. FIG. 3 shows a system 20 comprising a first roller 22 and asecond roller 24. The first 22 and second 24 rollers are positioned at afirst position in the production cycle, which is upstream from a secondposition where laminating rollers 28 are positioned. The laminatingrollers 28 are adapted to laminate the layers of film together into onefilm comprising two or more layer. This may be done e.g. throughpressing the materials together extremely tightly, using adhesive agentsand/or heat, and other similar laminating technologies aimed at joiningmultiple layers of materials together.

The first roller 22 is adapted to feed a first film layer comprising anelastic material, and the second roller 24 is adapted to feed a secondfilm layer comprising a sturdy material. The first roller 22 is adaptedto run at a speed v1. The second roller 24 is adapted to run at a speedhigher than that of the first roller 22, shown as v2. The laminatingrollers 28 are also adapted to run at the second speed v2.

The speed with which the materials are fed towards the laminatingrollers 28 is constant for each material, even though the speed ofindividual rollers may differ. The speed with which the films is fed bythe laminating rollers 28 is also constant. Depending on the exactstructure of the system, this may entail slight variations in howrollers are configured. If the rollers comprise a stack of materialwhich is wound around an axis and the unwound as the material is fed,the rotational speed of the roller would have to continuously increaseslightly to maintain a constant feeding speed, as the diameter of thewound material decreases due to the material being fed towards thelaminating rollers 28.

Due to the speed of the rollers differing, the first layer of the filmwill be stretched but second layer will not be. Since the first roller22 feeds its material towards the laminating rollers 28 at a first speedv1, while the laminating rollers 28 feeds the film in the feedingdirection at a second speed v2, wherein v2 is higher than v1, theelastic material will be stretched. This is due to the difference inspeeds that occurs at the second position, i.e. at the laminatingrollers 28. Since the feeding speed of the laminating rollers 28 ishigher than the feeding speed of the first roller 22, the material willbe stretched at the second position. As for the second roller 24, thesturdy material being fed by the second roller 24 is not stretched,since the feeding speed of the second roller 24 is the same as thefeeding speed of the laminating rollers 28, i.e. v2.

The second roller 24, however, operates at the same speed as thelaminating rollers 28, which entails that the sturdy layer of the film,which is the one fed by the second roller 24, is not stretched duringthe manufacturing process. Typically, the system is adapted such thatthe elastic material is stretched by an additional 10-50% as compared toits original state, but in some embodiments it may be higher, such as upto 300%. Optionally, the system 20 may also comprise a coil 30 ontowhich the film may be wound.

In some embodiments, the system 20 comprises three rollers instead oftwo. This is shown in FIG. 4. In this embodiment, the system furthercomprises a third roller 26. Typically, the third roller 26 ispositioned such that the second roller 24 is disposed between the firstroller 22 and the third roller 26. The third roller 26 is, like thefirst roller 22, adapted to feed a film layer comprising an elasticmaterial. The third roller 26 runs at a speed v1, same as the firstroller 22, which results in that the film layer fed by the third roller26 is stretched in the same way that the film layer fed by the firstroller 22 is. This results in a film comprising three layers, whereinthe two outer layers are stretched and comprise an elastic material,while the middle layer comprises a sturdy material. The layers that arestretched are typically stretched in the same direction as the film isbeing fed, which is the longitudinal direction of the resulting film.

Looking now at FIG. 5, the method according to the present disclosurewill be described. The first step S100 comprises providing andstretching a first film layer, typically comprising an elastomericmaterial such as low density polyethylene. By stretching the material,it strives to go back to its un-stretched state, which results in thematerial wrapping very tightly around the object around which it iswrapped.

The second step S110 comprises providing a second film layer, the secondfilm layer comprising a sturdy material such as woven plastic material.

The final step S130 of the method comprises laminating the layerstogether to form one film comprising two layers, wherein the firstlayers is stretched and the second layer is not.

In some embodiments, the method further comprises a step S120 ofproviding and stretching a third film layer, the third film layer alsocomprising an elastic material. This step may be seen in FIG. 6. In thisembodiment, the second film layer is typically provided between thefirst film layer and the third film layer, and the step of laminatingthe layers comprises laminating three layers instead of two.

Although the description above contains a plurality of specificities,these should not be construed as limiting the scope of the conceptdescribed herein but as merely providing illustrations of someexemplifying embodiments of the described concept. It will beappreciated that the scope of the presently described concept fullyencompasses other embodiments which may become obvious to those skilledin the art, and that the scope of the presently described concept isaccordingly not to be limited. Reference to an element in the singularis not intended to mean “one and only one” unless explicitly so stated,but rather “one or more”.

1. A film for wrapping of objects, comprising: a first film layer made from an elastic material, a second film layer made from a durable material, a third film layer made from an elastic material, wherein the second film layer is disposed between the first film layer and the third film layer, and the first film layer and the third film layer are stretched in a longitudinal direction.
 2. The film according to claim 1, wherein the first and third layers are stretched by 10%-50%.
 3. The film according to claim 1, wherein the second layer is made from a woven plastic material.
 4. The film according to claim 1, wherein the first and third layers are made from low density polyethylene.
 5. A system for manufacturing a film for wrapping of objects, comprising: a first roller running at a first speed positioned at a first position, the first roller adapted to feed a first layer film comprising an elastic material; a second roller running at a second speed positioned at a first position, the second speed being higher than the first speed, the second roller adapted to feed a second film layer comprising a durable material; laminating rollers positioned at a second position, the second position being downstream of the first position; wherein, the system further comprises a third roller running at the first speed, positioned at a first position, the second roller is disposed between the first and the third roller, and the laminating rollers are adapted to laminate the three layers into a film comprising three layers.
 6. A method for manufacturing a film for wrapping of objects comprising the steps of: providing and stretching a first film layer comprising an elastic material; providing a second film layer comprising a durable material; providing and stretching a third film layer comprising an elastic material, wherein the second film layer is provided between the first film layer and the third film layer, laminating the layers together to form a laminated film, wherein the stretching is performed in the longitudinal direction of the film. 